Annular bi-component spinerette assembly



Dec. 3, 1968 R. 1.. YELVERTON, JR 3,413,683

ANNULAR BI-COMFONENT SPINNERETTE ASSEMBLY Filed Sept. 24, 1965 6Sheets-Sheet l INVENTOR. ROY L. YELVERTO/V JR.

ATTORNEY Dec. 3, 1968 R. L. YELVERTON, JR 3,413,683

ANNULAR BI-COMPONENT SPINNERETTE ASSEMBLY 6 Sheets-Sheet 2 Filed Sept.24, 1965 I L I INVENTOR. ROY L. YELVERTO/V JR.

ATTORNEY Dec. 3, 1968 R. L. YELVERTON, JR 3,413,633

ANNULAR ELI-COMPONENT SPINNERETTE ASSEMBLY Filed Sept. 24, 1965 6Sheets-Sheet 3 INVENTOR. R0) L. YE L V5 R TON JR.

A TTORNEY R. L. YELVERTON, JR 3,413,683

ANNULAR BI-COMPONIZNT SPINNERETTE ASSEMBLY Filed Sept. 24, 1965 6Sheets-Sheet 4 INVENTOR. ROY L. YELVERTON JR.

ATTORNEY 1968 R. YELVERTON, JR 3,413,683

ANNULAR BI-COMPONLNT SPINNERETTB ASSEMBLY Filed Sept. 24, 1965 6Sheets-Sheet 5 INVENTOR. R0) L. YELVERTO/V JR.

ATTORNEY Dec. 3, 1968 R. L. YELVERTON, JR 3,413,633

ANNULAR BI'COMPONENT SPINNERETTE ASSEMBLY Filed Sept. 24, 1965 6Sheets-Sheet 6 INVENTOR. ROY L. YE'LVERTON JR.

A 7' TOEWE Y United States Patent 3,413,683 ANNULAR BI-COMPQNENTSllNERETIE ASSEMBLY Roy Lee Yelverton, .Ir., Gulf Breeze, Fla, assignorto American Cyauamid Company, Stamford, Conn, a

corporation of Maine Filed Sept. 24, 1965', Ser. No. 490,651 2 Claims.(Cl. 18-8) ABSTRACT OF THE DISCL'BSURE For spinning economically largenumbers of bicomponent fibers from each spinning position, an annularbicomponent spinnerette is provided having a novel spin dopedistribution assembly associated therewith.

This invention relates to an improved circular extrusion head formulti-component extruded filaments and, more particularly, forbi-component extruded filaments.

Synthetic fibers, which are achieving rapidly increasing use, are madeby extruding polymer into a coagulating or cooling medium. There are, ingeneral, three processes. One is melt extrusion, where the materialswhich form the final filaments are melted and extruded throughspinnerettes into a medium which is colder and which may be colder air,a coagulating bath, and the like. The second method is the so-called dryspinning method, in which the materials forming the fiber are dissolvedin a solvent of suitable volatility and are then extruded throughspinnerettes into a hot atmosphere which may be air, the solvent rapidlyevaporating, and the filament solidifying after it leaves thespinnerette nozzles. The third method is the so-called wet spinningmethod, in which the polymer is dissolved in a solvent and extrudedthrough a spinnerette into a coagulating bath, which causes the materialto coagulate. The wet gel is washed free of solvent, stretched and driedto form the final filament. The coagulation may be by dilution of thesolvent, chemical action on the materials extruded, or temperature. Veryfrequently the action of the coagulating bath may be a combination ofdilution and temperature change. In the specific example of filamentformation which will be described below and which deals withbi-component acrylic fibers, the COag' lating bath is much colder thanthe temperature of the extruded dissolved material and also results indilution, because in this case the spinning solution is a hot aqueoussalt solution of polymer and the coagulating bath is a cold saltsolution with excess Water. Coagulation takes place, therefore, both bytemperature change and by dilution of the solvent. Since the presentinvention relates to an apparatus and broadly also to an extrudingprocess for wet spinning, the particular mechanism of coagulation in thebath into which the filaments are extruded is more or less immaterial;and the invention, therefore, is not limited to the wet spinning of anyparticular solutions into any particular coagulating bath. The specificexample which will be described is only a typical use of the invention,although a very valuable one, and is intended to be illustrative only ofthe operation of the invention.

Extruded fibers are produced in two general forms: continuous filament,in which the extruded filament is formed in continuous lengths, thoughsometimes a thread may have a number of filaments; and the so-calledspun threads, which are produced from relatively shorter pieces offilaments, which are frequently referred to as tow or staple. It is withthe latter type of synthetic fiber threads that the present invention ismost commonly used, but the extrusion of multi-cornponent, continuousfilament yarn is not excluded. In the past, when staple or tow wasproduced the fibers were machanically crimped,

'ice

somewhat in the form of the crimps on a hobby pin, in order to produce asutiicient amount of cohesion to permit textile processing. The spunthread or yarn is then made into fabrics and usually in the finishing ofthe fabrics they are subjected to heat, such as hot water, steam and thelike, which takes out the remaining mechanical crim leaving the spunyarn with the individual fibers substantially straightened.

The yarns spun as described above have achieved widespread commercialuse, but there is a demand for a bulkier yarn, for two reasons amongothers. First, the bulkier yarn has a softer feel or hand and, secondly,in many cases the bulkier yarn has greater covering power per unitweight, with of course a saving in cost. In order to produce a bullrieryarn it has been proposed to extrude multi-component and, preferably,bi-component fibers, the two components having slightly different ratesof shrinkage. These multi-cornponent fibers, which in the balance of thespecification will be referred to as bi-component fibers in accordancewith the preferred form, tend to curl or crimp on relaxation fromstretching and when such fibers are made up into yarns the curl resultsin a bulkier and softer yarn. For textile processing purposes, after thefibers have been extruded from a spinnerette into a suitable coagulatingbath they are usually stretched. If they are allowed to relax and curl,the crimp frequency and amplitude usually are too extensive forsatisfactory textile processing, and therefore it is common to removethe curl temporarily by stretching under suitable conditions and thenmechanically crimping for spinning purposes. The spun yarn either beforeor after being formed into a fabric is then subjected to heat andcooling, for example by hot water, and on cooling the individual fiberscurl and the bulky yarn results. The present invention deals only withthe extrusion of the oi-component threads, and the further treatment,spinning and the like, is not significantly changed by the presentinvention. The extrusion of bi-component filaments, however, presentedquite serious mechanical and operating problems, for the spinneretterifices were extremely tiny, for example a small fraction of amillimeter for 3 denier filaments. To proportion accurately two streamsof the different filament components was a formidable problem. This canbe well appreciated when one considers that a commercial spinnerette forwet spinning tow may have from 5,000 to 20,000 or more orifices.

A successful approach to the problem above presented is described andclaimed in the patent to Fujita Shimoda and Zoda, No. 3,182,106, May 4,1965. In this patent each orifice in the spinnerette plate of theextrusion head was flared on its inner side to produce openings muchlarger than the final spinnerette orifice. This also had the additionaladvantage of spacing the orifices sufficiently so that the extrudedfilaments did not tend to stick to each other and the coagulating bathcould reach all of the circumference of each filament. The back of thespinnerette plate showed the enlarged or flared orifices tangent to eachother in rows. A guide plate back of the spinnerette plate had channelscommunicating with the rows of orifices in the spinnerette plate, andbehind this were mounted septa along each row, which, in effect, withthe plate defined a Y-sh-aped channel, the sharp edges of the septa ofcourse being aligned with the center of the orifice openings in the backof the spinnerette plate. Supply manifolds were provided so that onesolution of material to be extruded flowed down one leg of the Y and theother down the other and joined and flowed in laminar fiow down throughthe stem of the Y and into the orifice openings in the spinneretteplate. This laminar fiow produced no substantial mixing of the normallyquite viscous spinning solutions, and so, a filament was extruded whichhad in cross section a semi-circle of one component and the othersemi-circle the other.

The present invention is not concerned with the exact shape and size ofthe spinnerette orifices. The semi-circular cross sections are, ofcourse, produced by round orifices. The size of the orifices isdetermined by a number of factors, including the cross sectional size ofthe fiber produced. For convenience the two different spinning solutionswere referred to as A and B, and this same convenient designation willbe followed in the present specification. The patent above referred toalso describes a refinement in the form of an extremely fine meshscreen, for example less than 200 mesh, immediately back of the orificeopenings in the spinnerette plate. This produced a very slight amount oflocal turbulence so that at the interface of the two semi-cylindricalfilament components there was very slight mixing, which prevented theseparation at the interface when the filament was coagulated.

The spinning process described above was successfully operative, but themechanical construction of commercial extrusion heads with manythousands of orifices presented a very severe problem. A majorbreakthrough to this problem was achieved by Douglas and Tonnies intheir application, Ser. No. 249,203, filed Jan. 3, 1963, and assigned tothe assignee of the present application. Here a large number of thinplates of different shapes in series of 3s or 4s were stacked to formthe septa and the distribution of manifolds of solutions A and B to thetwo sides respectively of each septum. If one looks at the extrusionhead lying on its edge, this meant that the thin plates were stackedvertically and they were generally referred to as a vertical stack head.For the first time, an economical practical commercial extrusion headfor thousands of orifices was produced. However, important as thebreakthrough was, problems were presented. The plates had to be alignedextremely accurately because, of course, their edges, forming the septa,had to be precisely aligned with the spinnerette orifices. Also, thevery thin plates were capable of bending and a serious problem waspresented when the head was disassembled for cleaning, which is aperiodic necessity in a practical commercial machine.

The next step for commercial extrusion heads is described and claimed inthe co-pending application of Sulich, Ser. No. 286,773, filed June 1 0,1963, now US. Patent No. 3,245,113, issued Apr. 12, 1966, and alsoassigned to the assignee of the present invention. Here the channels,including spin solution manifolds, dividers, septa and the like, werearranged in horizontal plates parallel to the face of the spinneretteplate, and this construction is known as the horizontal stack head.

Problems of alignment of the various plates when the head isdisassembled for cleaning were completely solved, but a problem remainedof accidental slight bending or warping of the very thin septa when thehead was disassembled for cleaning. This problem was at least as acuteas in the vertical stack head, although the initial alignment of theplates presented no problem. The horizontal stack head, except for thegreat care needed to prevent bending of the septa in cleaning, overcamethe disadvantages of the vertical stack; but now another problem arose.

With an extrusion head having many thousands of spinnerette orifices,the coagulating bath has to pass from the outside of the rope ofextruded filaments into its center. In such passage the temperature ofthe coagulating bath changes, because in many cases the spinningsolutions are quite hot, for example a temperature difference of 60 C.and more from the approximately C. coagulating bath in the case ofacrylic fibers extruded into aqueous thiocyanate baths, as described inthe specific example below. Also, in this case, and the same 1s true formany other wet spinning processes, the chemical nature of the bathchanged, because in coagulating the thiocyanate content of thecoagulating bath increased, and in the case of other coagulating bathsdifferent chemical changes may result. As a result, the filaments nearthe center of the rope did not coagulate at the same rate as thosenearer the outside, and this problem is referred to in the art as whitecore.

The problem was not so severe that extrusion heads could not be used,but it required a wider tolerance for practical acceptance and so was adistinct practical disadvantage. It is more particularly with a solutionto this problem and the elimination or great reduction of bending ofsepta during cleaning that the present invention relates. The presentapplication may, therefore, be considered as an improvement on theSulich application; but it should be noted that the problems solved arereally acute only with extrusion heads for commercial machines whichhave thousands of orifices. The problems do not arise, at least insevere form, in laboratory machines which may have extrusion heads ofonly a hundred or a few hundred orifices. The present invention is,therefore, an improved head for practical commercial machines and not anew principle which is needed in all sizes of extrusion heads, even forlaboratory machines.

In the horizontal stacked head of the Sulich application, it wasnecessary to provide certain'stitfening or supporting ribs to the platein which the septa were formed. These resulted in some channels, as ofcourse there were no orifices in the spinnerette plate opposite theribs. To a very small degree, these channels helped with the white corerope problem, but the help was too small to be of any practicalsignificance either in the rectangular form of extrusion head or in thecircular form, which are both shown in the Sulich application. As amatter of fact, there is somewhat greater help in the white core problemin the rectangular head than in the circular head. However, even therethe improvement is so slight that for practical purposes the differenceis insignificant, so that in practical machines no distinction is madewhatsoever between the two shapes of heads as far as white core problemsare concerned.

The present invention utilizes horizontal stacking, but the plates areneither rectangular or circular, they are annular. The extrusion head,therefore, has a large central conduit through which fresh coldcoagulating bath is continually circulating. The outer shape of the headwould not theoretically need to be circular, it could be square; but asthis would only increase manufacturing costs and slightly decreaseefficiency, practical extrusion heads according to the present inventionare made up of elements which are pure annuli with concentric inner andouter circular peripheries. However, in the specification and claims,the term annular will be used in a slightly broader sense as shapes inwhich the central opening and the outer periphery form concentric curveswhich, however, do not have to be pure circles, although for practicalpurposes nothing is gained by departing from the ideal perfect annularshape.

In addition to the presence of a central, relatively large conduitthrough which coagulating bath can flow, the present invention does havecertain general, though not sharply critical, dimensional relationships.Thus an annular head with a minute central opening is no better than ahead with no opening at all, and it is of importance that the distancefrom the outer periphery of the annulus to the inner be sufiicientlysmall so that the number of rows of orifices is not excessive. Forpractical operating machines the cross sectional area of the centralchannel should not be significantly less than 5% of the area of theannular part of the extrusion head in which the orifices are located.Excellent results are obtained with bi-component acrylic polymers whenthe area is from about 10% to about 12% of the annular area of the headcontaining the orifices. Theoretically there is no upper limit on thepercentage, but as a practical matter, it will rarely be desirable tohave an area more than about 15% of the annular area, because if it istoo big the overall size of the head for a given number of extrusionorifices becomes uneconomically large, although of course perfectlyoperative.

The effectiveness of the introduction of coagulating bath through thecenter opening is so great that, as will be described at the end of thespecification in specific tests, it is possible to introduce all of thebath through the central openings, with none being introduced around theextrusion head. It is, of course, preferable to have bath on both sidesof the tubular rope of filaments which results, but it is quitesurprising that, as an extreme test, the introduction through thecentral opening alone permits operation at speeds substantially as greatas when the bath is introduced also around the extrusion head.

Another important advantage of the present invention is a greatlyincreased pull-away of the filaments from the extrusion orifices, whichpermits satisfactory operation at considerably higher speeds. This is anadvantage which can be enjoyed in two difierent ways. Thus with the samequality of extruded filaments, higher speed can be used, or with thesame speed, an enormously greater factor of safety can be enjoyed. Inpractical operating machines a compromise is usually chosen, increasingthe speed markedly while at the same time not going to the limit, so asto increase relia ility of operation. The best particular compromise inthis respect will be chosen in each case in conjunction with theoperating requirements, which include not only the nature of thematerial extruded but also its cross-sectional size. Different sizes offilaments also have an effect on the range of central openings which arepermissible. As a general thing, coarser filaments, such as for examplecarpet threads, present a more serious problem of white core than dofiner threads, and for this reason, in the specii c tests described atthe end of the specification, the use of relatively coarse threadspermits quite drastic testing of the advantages of the presentinvention.

The movement of the filaments through the coagulating bath serves topull the bath along with it. In other words, they exert a pumpingaction. it is, therefore, ordinarily not necessary to use pumps whichcirculate bath at high speeds. Generally it is sufilcient to pump inbath at a rate such that it will not be degraded by warming up, changeof chemical concentration, and the like; and the flow through aconventional bath chamber is quite largely effected by the pumpingaction of the filaments. In this connection, it should also be notedthat there is a much stronger pum ing action on the bath enteringthrough the central opening than that around the outer surface of thetubular rope of filaments. This pumping effect increases markedly thereliability of operation and is one of the factors permitting operationat higher speeds.

It mi ht at first be thought that the present invention woulddrastically reduce the number of orifices in an extrusion head of givensize. However, since the number of orifices is very much greater in theouter rows than in the center, this does not reduce their numbersignificantly or, if it is essential that the same number of orifices bepreseat, a head of only VCI'j moderately increased outer circumferenceis needed. That the great advantages of the present invention areobtainable without significant reduction in number of orifices or withonly very slight increase in size constitutes an important advantage ofthe present invention.

The generally annular arrangement of the orifices is not critical. Therows may be perfect circles, each having a septum which is continuousaround the row. Other designs are possible, such as radial septa andholes. In such cases the holes need not be exactly in perfectlyconcentric circles. It is sufiicient that the rows of holes form anannular band.

The preferred pure annular shape of the plates has an additionaladvantage. The septa now are cylinders fastened to a rigid fiat plate.This is both easy to produce mechanically and it reduces the possibilityof slight bending or warping of the septa when an extrusion head isdisassembled for cleaning to a very significant extent. When supportedat one end, a cylindrical surface represents a maximum of stiffness andso, the problem of septa bending which, although reduced over thevertical stacked extrusion head by the horizontal stacked head, stillexisted is solved in the present invention, and it is solved by reasonof the shape and design of the invention and not by the addition offurther elements. The stiffness of the cylindrical septa can be wellvisualized when one considers that these septa are very short, in otherwords they form cylinders which are extremely short in comparison totheir circumference. As one end of each cylinder is rigidly mounted oreven integral with a still flat plate, a very high degree of stiffnessis obtained so that the possibility of septa bending on disassemblingand cleaning is, for all practical purposes, completely eliminated.

The invention will be described in greater detail in conjunction withthe drawings, in which:

FIG. 1 is an exploded view of the plates forming the stack of onemodification;

FIG. 2 is a cross section through a stack taken on the line 22 of FIG.6;

FIG. 3 is a section along the line 33 of FIG. 5;

FIGS. 4A and 4B are cross sections along the lines 4A 4A and 4B4Brespectively of FIG. 5, both at right angles to the section of EEG. 3;

FIG. 5 is a plan view, partly broken away, of two plates forming thedistribution element for different solutions;

FIG. 6 is an elevation of the front view of the primary distributionplate;

PEG. 7 is an exploded view of a stack similar to FIG. 1 but showing amodified final distribution plate, and

FIG. 8 is a rear view, partly brokn away, of a portion of thedistribution plate of FIG. 7.

Turning to FIG. 1, it shows the principal elements of a stack inexploded form with the exception of a screen just back of thespinnerette orifices which does not show in this figure but can be seenin FIG. 2, as will be de scribed below. The stack is made up of six mainelements, a primary solution distribution plate 1 provided with externalthreads 18, an intermediate plate 2 with two rows of staggered holes 22and 23, a final distribution element in two pieces 3 shown partly brokenaway in FIG. 1 and in more detail in FIGS. 3, 4A and 4B, an orificeplate 4 with orifices 20, an outer clamp ring 5 with a tapered skirt 1?.with internal threads 19 and an internal clamping element 6 with a clampflange d, separate body It and external threads 9. It will be seen thatas all of the elements of FIG. 1 are annular, when the stack is clampedtogether, as is shown in FIG. 2, there is a central passageway, showngenerally at 7, which flares at its rear end where the tapered portionof the body 16 of the element 6 screws into the internal theads 11 ofplate 1. This will be seen best in FIG. 2.

The stack will be described in connection with its operation with twosupplies of polymer solutions of different shrinkage characteristics.These solutions will be labeled A and B in all of the figures inaddition to the numerical labeling of the actual elements of each plate.The two solutions A and B enter through pairs of pipes 13 and 15 inplate 1. This is best seen in FIG. 6, although FIG. 2 shows some of theelements in cross section. It will be seen that plate 1, looking at itfrom the front, is provided with two concentric grooves 14 and 16 whichextend around a full circumference of the plate 1. It will be seen fromFIG. 6 that solution A entering through the pipes 13 flows into theouter groove 14 whereas solution B, entering through pipes 15, flows outinto groove 16.

Plate 2 mounts on the face of plate 1 with the outer ring of holes 22registering with the groove 14 and the inner row of holes 23 registeringwith the groove 16. Plate 2 transforms the grooves 14 and 16 intoconduits. Solutions A and B pass from the conduits through plate 2,through the holes 22 and 23 respecetively.

FIG. shows a front view, broken away to illustrate its three levels. Therear-most level, which is shown at the right, is provided with oblongopenings 24 and 25. These openings alternate and the openings 24 extendradially beyond the ends of the openings 25. The alignment is such thatthe openings 24 communicate with the staggered holes 22 of plate 2 andat their opposite end extend sufficiently to communicate with elementsin the middle level of plate 3, as will be described below. The openings25 are shorter and communicate with the inner row of holes 23 of plate2. Therefore, the openings 24- will be filled with solution A and theopenings 25 with solution B. The solution labeling is repeated for thefirst four openings in FIG. 5. The openings 24 and 25 are reallydepressions in the rear-most portion of the plate 3 which is showngenerally at 26 in FIGS. 3, 4A and 4B, as well as FIG. 5. It will beapparent that the plate 2 closes the rear of the depressions 24 and 25transforming them into cavities with inlets from the holes 22 and 23 ofplate 2 respectively.

Turning now to FIGS. 3 to 5, it will be seen that there are concentricinterrupted openings 27 and 28, as will be seen from FIG. 5. Thesegrooves are flared, FIGS. 4A and 4B. The appearance on FIG. 5 that thegrooves would extend into two chambers 24 and 25 is because the flaredportion is seen, but the grooves do not extend into these two chambers,since each only communicates with a single chamber.

The front level of plate 3 is shown at 29 in FIG. 3. It also appear inthe section in FIG. 2, but the illustration is clearer in FIG. 3, whichis to a larger scale. The openings 27 are opposite solid portions 30,and corresponding solid portions 31 are opposite the openings 28. Thesesolid portions are staggered, as appears more clearly from the left handportion of FIG. 5 and FIGS. 4A and 4B.

In the front plate 29 are also machined septa 32 which are in the formof short concentric cylinders. Each septum is opposite the center of anannular row of spinnerette holes 20 of spinnerette orifice plate 4. Itwill be seen from a consideration of FIGURES 2, 3 and 5 that differentstreams A and B of polymer solutions flow on different sides of eachseptum. With the orific plate 4, the septa define annular channelsthrough which the different polymer solutions flow. The particularsolutions A and B are shown for a few septa in FIGS. 3, 4A and 4B, andthe flow of solution B appears most clearly from FIG. 3, whereas theupper portion of FIG. 2 shows the flow for solution A. For clarity, onlya few septa are shown in FIG. 2. It will be seen from FIG. 2 that a veryfine mesh screen 21, for example a ZOO-mesh screen, is between the edgesof the septa and the orifices in the back of plate 4. This screenproduces slight turbulence at the interfaces of the streams of the twopolymers.

The spinnerette stack, as shown in FIGS. 1 and 2, ex trudes into acoagulating bath, as has been described above. It will be seen,particularly from FIG. 2, that there is a fairly wide central passagethrough the spinnerette stack. Through this passage coagulating bathflows. The filaments are extruded in the form of a hollow tube,coagulating bath flows between them both from the outside and from theinside, as described above. The travel transversely through the tube offilaments is sufficiently short so that there is no substantial changein the characteristics of the coagulating bath for different fibers, andtherefore the problem of White core is solved. The great effect of theshort travel will be discussed below in connection with specific tests.

It will be seen from FIG. 3 that the septa are machined into the solidplate 29. They are, therefore, in the form of low, concentric cylinderswith one end part of a rigid backing plate. This gives the septa themaximum strength against bending and greatly reduces or completelyeliminates problems of bending of septa when the head is disassembledfor cleaning, which, as has been pointed out above, must be effectedperiodically in practical machines. At the same time, the automaticalignment of septa with rows of orifices is fully maintained. In otherwords, all of the advantages of the horizontal stack spinnerette headsof the Sulich application referred to above are shared by the presentinvention. This represents an unusual and advantageous situation,because generally when apparatus is modified to eliminate one drawback,this is at the expense of certain other features. In other words,usually a compromise results. In the present case the importantadvantages of the solution of the white core problem and maximuminsurance against bending of septa on cleaning are obtained without anyoffsetting disadvantages.

FIGS. 1 to 6 represent a very economical form of the invention in whichthe final distribution plate or element is made up of several portionsand lends itself to cheap and simple fabrication. FIGS. 7 and 8illustrate a modification which operates in the same way with maximumrigidity of the final distribution plate but which presents thedisadvantage of somewhat more expensive machining or fabrication. As theplates or elements 1, 2, 4, 5 and 6 are the same as in FIG. 1, they bearthe same reference numerals. The flow of solutions A and B through themis also the same, and the description will not be repeated. However, thefinal distribution plate or element 33 is different and is illustratedin detail in FIG. 8, which shows part of the element broken away,exposing three different levels. Contrary to the element 3 of theearlier figures, this plate is in one piece, and FIG. 8 shows a viewfrom the rear and not from the front, as is the case in FIG. 6. The rearface of the plate is provided with depressions 34 and 35 which, thoughslightly different in shape, perform exactly the same functions as thecorresponding elements 24 and 25 of FIG. 5. In other words, with theplate 2 they form conduits or chambers which communicate with thedifferent staggered holes 22 and 23 of plate 2. In the same manner, theresulting chamber 34 receives solution A and 35 solution B.

Looking at the portion of FIG. 8 immediately to the left of center, itwill be seen that there are a radial series of slots 36 and 37. Themetal between the slots in the rear portion of the plate, shown to theright of the central break in FIG. 8, assumes the form of a sinuousbaffle 38. It will be seen that this bafiie directs solution A from achamber 34 into the slots 36 and solution B into the slots 37.

The front face of the plate 33, which appears at the extreme left ofFIG. 8, has concentric septa machined in, the septa being the same shortcylinders as appear in FIG. 5, but they are machined integrally in asingle plate instead of a separate element. As the septa constitute thesame type of element and perform the same function as in FIGS. 2, 3 and5, they are designated by the same reference numeral 32.

As the alternate slots 36 and 37 receive solutions A and B respectively,as has been described above, it will be apparent that the two solutionsflow on the different sides of each septum in exactly the same manner asin the modification shown in FIGS. 1 to 6. In other words, plate 33,although of different mechanical construction, performs exactly the samefunction as the multiple element, distribution plate 3 of FIGS. 1 to 6.While plate 33 is illustrated as a single, unitary structure, it can befabricated as a multiple structure element. The feature of the sinuousbaffie would still be retained. While the modification of FIGS. 7 and 8may be somewhat more expensive to make, when in the single, unitary formit operates with the same efficiency and, in fact, as far as bending ofthe septa is concerned, it is, if anything,

9 more rigid than the modification of FIGS. 1 to 6. As, however, therigidity of the septa in the earlier modification is entirely adequate,multiple element plates may be preferable wherever they are cheaper tomanufacture.

It should be noted that in its broader aspects the present inventionrequires means for distributing the two polymer solutions on either sideof each cylindrical or concentric septum, and the final distributionplates 3 and 33 represent only two possible mechanical distributionmeans. They are, therefore, illustrative only, though in a more specificaspect they constitute desirable mechanical structures.

While the apparatus of the present invention, as such, is not concernedwith the exact chemical nature of the solutions of filament-formingmaterial, except insofar as they must have suitable viscosities, atypical illustration of the process aspect of the present invention isas follows:

Using the apparatus of FIGURES 1 to 6, dissimilar solutions ofacrylonitrile polymer dissolved in hot concentrated aqueous sodiumthiocyanate (solutions A and B, previously identified) were pumped intopipes 13 and 15 to extrude bi-component filaments from orifices aspreviously described. Cold dilute aqueous sodium thiocyanate flowingthrough channed 7 and around the extrusion head rapidly coagulates thefresh extrudate by cooling and dilution to form wet gel bicomponentfilaments.

Because of the relatively small distance through the moderate number ofrows of extruded filaments, they are uniformly bathed in the coldcoagulating bath. The length of travel is insufiicient to changesignificantly the temperature of the bath or to produce too high a thiocyanate content. After the filaments are coagulated they are washed inwater, stretched, and dried in the usual manner. As this portion of theoperation is not significantly changed by the present invention, it willnot be further described in detail. When the present invention is usedto produce other multi-component filaments, the nature of the solutionsand of the filament-forming materials will of course be different.However, in every case the advantages of relatively short travel of thecoagulating bath through the tubular rope of filaments are obtained.

In order to test out the effects of varying proportions of cross sectionof the central conduit and the annular face of the extrusion head, ahead for very coarse carpet thread was used, which represents a severeproblem in coagulation. T o produce a tow of about 16.5 denier carpetfiber, a spinnerette having 3108 orifices each having a diameter of 150was used. The cross-sectional area of the whole box containing thespinnerette and coagulant bath was 79.1 in. the annular portion of thespinnerette head 36.8 in. and the center hole 3.8 in. In other words,the ratio of area of the center opening to annular face was just over10%. No problems of white core resulted and spinning was excellent.

When the ratio dropped below 4.6%, satisfactory operation no longer tookplace. In other words, under the conditions of the test, for safe,practical operation the ratio should not be significantly below 5%.

The etfect of fiow through the central orifice was tested qualitativelyby blocking off any flow around the outer periphery of the extrusionhead. Because the back of the bath container overflowed under suchconditions, it was not possible to maintain the full fiow through thecentral orifice. Nevertheless, although the flow was substantially lessthan used previously, spinning conditions were normal, there were nobroken filaments or capstan Wrap-ups. This was, of course, an extremelydrastic test, showing the enormous effect of the bath going through thecenter opening. For practical operating machines, such conditions wouldbe ridiculous and so, the extrusion heads of the present invention willnormally be used in practical operation with bath flowing both throughthe central opening and around the edges of the head.

When the speed of extrusion was increased to 125% of that used in theprior tests, excellent results were obtained, other conditions remainingconstant, whereas with an ordinary head, as described in the Sulich orDouglas and Tonnies applications referred to above, such increased speedresulted in unsatisfactory operation.

Comparison tests were conducted to see whether the salt concentration inthe coagulation bath could be increased above that previously used. Itwas found that the salt concentration could be increased as much as 50%without encountering white core problems. Operation of the processingequipment with increased salt concentration in the coagulant reduces thesteam load on the evaporators by reducing the amount of water to beevaporated in reconcentrating the coagulant for reuse in preparingspinning solutions. This is an important economic advantage of thepresent invention.

When coagulant flows into a bundle of freshly extruded filaments, theconcentration of the coagulant rises as it extracts salt from thecoagulating filaments. In order to avoid the white core problem, thecoagulant concentration should not be permitted to rise above a certainmaximum so no single filament gets exposed to too high a concentrationof coagulant. Since the coagulant concentration rises as the coagulantpenetrates the fiber bundle, the coagulant fed to the spinning apparatusmust have a low enough concentration to allow for this rise withoutreaching that level at which the white core problem exists. Since theflow path of coagulant through the fiber bundle is greatly shortened bythe present invention, the concentration rise in the coagulant isgreatly lessened. Thus, the coagulant fed to the spinning apparatususing the present invention can be much higher (up to 50% higher)without defective filaments due to improper coagulation.

Comparison tests were made to show the effect of eliminating thesolution distribution plates and as, of course, bi-component filamentscannot be produced without distribution plates, the spinning was ofsingle-component filaments. This does not change significantly theresults. The spinnerette used had 10,308 holes of p. diameter. First,spinning was effected with the distribution plates eliminated and thenwith them added. The addition increased the maximum speed at which itwas possible to spin by approximately 50%.

A comparison test was made with a vertical stacked ead according to theDouglas and Tonnies application referred to above, and the maximum speedpermissible when making bicomponent fibers was only a little over halfas great as when making bicomponent fibers using the present spinneretteassembly.

It is not known why the distribution elements of the present inventionalso permit higher speeds, and it is not desired to limit the presentinvention by any theoretical explanation. However, the results arepractically valuable and show that the present heads, even if used witha single spinning solution, though introduced of course as two streamsuniting in the orifices, improved results are obtained, which is apractical advantage as it is possible to shift from a run withbi-component threads to one with mono-component where the exigencies ofa particular operation make this additional versatility desirable. Theimproved results are, of course, not as spectacu- Iar or as important aswhen bi-component filaments are spun, but it is an additional advantageof the present invention that the heads are also better even formonocomponent operation.

I claim:

1. In an annular spinnerette assembly comprising an annular spinnerettehaving a plurality of orifices disposed in concentric circular rows,means to introduce two separate spinning solutions thereto, and anannular distributor mounted adjacent said spinnerette to keep separatesaid two spinning solutions until just prior to flowing both saidspinning solutions side-by-side through each orifice of saidspinnerette; the improved distributor comprising an annular plateprovided with (a) a plurality of annular septa defining a plurality ofannular spinning solution channels in one face thereof, (b) a pluralityof slots in the base of each such channel extending through suchdistributor, such slots being disposed in radial arrays with each suchslot in any single such spinning solution channel being adjacent to andsubstantially coextensive with the slots in the next adjacent spinningsolution channels, and (c) means to direct the two spinning solutionsalternately into slots in alternate spinning solution channels.

2. A spinnerette assembly as defined in claim 1 wherein said last meanscomprises recesses in the other face of said distributor separated bysinuous bafiies which snake around each said radial array of slots sothat alternate slots connect with one recess and the remainder of saidslots connect with the adjacent recess, and means to separately supplydifferent spinning solutions to each pair of such adjacent recesses.

References Cited UNITED STATES PATENTS 2,047,313 7/ 1936 Dreyfus 18B2,536,092 1/1951 Roberts 188 3,245,113 4/1966 Sulich 188 3,248,4664/1966 Woodell 264168 X 3,341,645 9/1967 Horiuchi et a1. 264-181 XJULIUS FROME, Primary Examiner.

J. H. WOO, Assistant Examiner.

